ME425/16599 Aerospace Propulsion
Coursework Exercise No.2: Engine Performance
Deadline: 1ST April 2022
The objective of this exercise is to calculate engine cycle conditions for the New Efficient Aircraft at
cruise and an off-design operating point taken to be take-off from sea-level. This calculation is very
similar to those carried out in the tutorial sheet 4 wherein most of the key engine variables were
calculated. The variables to be calculated are listed in the table below and included: pressures and
temperatures throughout the engine, key pressure and temperature ratios, by-pass ratio, core and bypass
jet velocities and the net and gross thrusts. There is no need to calculate physical parameters of the
engine such as diameters or rotational speed. The input/design conditions for cruise are as follows:
To make your calculations more realistic you should account for the different flow compositions and
temperatures in the various parts of the engine. Specifically, in the compressor and bypass duct you
may take: Cp = 1005 J/kgK and 𝛾 = 1.4 whereas in the turbine and core nozzle you should use: Cp =
1244 J/kgK and 𝛾 = 1.3. However, you may neglect the fuel mass flow rate under both cruise and
take-off conditions and regard combustion merely as the addition of heat. You should also use
polytropic rather than isentropic efficiencies and may assume a value of 0.9 for all components.
(Hint: assuming the by-pass jet velocity equals core jet velocity)
When calculating conditions for take-off you may assume that the ratio To4/To2 takes the same value
at cruise and under take-off conditions although since the Mach number will not be a constant this is
not simply a scaled cruise condition. You should check to see if the thrust generated would be enough
to take-off safely in the event of the loss of an engine at take-off. To make this assessment you may
assume that at take-off the speed of the aircraft is 90m/s, the lift to drag ratio is 10 and that the minimum
acceptable climb rate is 3m/s vertically.
(Hint: 1. assuming booster temperature ratio and HP turbine temperature ratio at Take-off are same
as that in the Cruise; 2. Assuming mass flow at turbine entry is same as that at turbine exit to find out
fan pressure ratio)
Boost temperature ratio=(T023-T02)/(T013-T02)
HP Turbine temperature ratio= (T04-T045)/T04
As for the previous coursework exercise, you should prepare an outline report illustrating how your
calculations have been conducted and bring it with you as a reference during a Myplace online
quiz. Once the quiz has been completed you should submit your report as evidence of your
working. There is no need for a formal report structure but you should include a cover page that states
the title of the module you are enrolled on, the coursework task title and your name.
As part of this exercise you should calculate at least the following values:
Marking Scheme
This piece of work forms 20% of the final mark for ME425 and 16599.
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